The present invention relates to a variable guide vane arrangement and configuration for high-load compressors, especially for use in gas turbine engines, wherein the guide vanes of at least one axial-flow stage are pivotally supported in the compressor outer casing by means of pivot pins and wherein the respective airfoil of the guide vane rests at least partially on a vane turntable connected to the pivot pin.
Variable guide vanes in variable-geometry compressors are normally designed such that, on the casing side, the airfoil rests fully or partially on a turntable which terminates at the pivot pin. While the pivot pin serves to adjust the longitudinal and circumferential position of the vane relative to the casing, the turntable maintains the position of the vane radially and primarily serves to eliminate or reduce the clearances between the vane and the casing. The diameter of the turntable varies with the number of guide vanes in the cascade and is normally selected such that the land remaining between adjacent holes or recesses for the turntables in the casing remains sufficiently thick and cannot be pushed into the adjacent hole during machining.
As is known, the number of vanes in a cascade depends largely upon the aerodynamic load. As the cascade load increases, the cascade pitch grows closer. For the reasons cited above, this will accordingly reduce the feasible diameter of the turntable. As a result, again, the length of the gap on the casing side increases (and the flow losses rise), and simultaneously the base on which the airfoil rests is reduced. The latter effect has a tremendous influence on vibrations and, therefore, the operational reliability of the components involved.